1. 1
   A road maintenance depot stockpiles rock salt (sodium chloride) ready to be spread on roads during icy weather. The depot's supervisor is training new staff on why salt is effective and wants them to understand the chemical structure of sodium chloride.

   (a)

   A road maintenance depot stores rock salt (sodium chloride) to grit icy roads in winter. Sodium chloride is formed when a metal reacts with a non-metal. What type of bonding holds sodium and chloride ions together in this compound?

   [1 mark]

   • ACovalent bonding
   • BMetallic bonding
   • CIonic bonding
   • DNo bonding, just a mixture

   (b)

   Sodium is in Group 1 and chlorine is in Group 7 of the periodic table. What happens to electrons when a sodium atom reacts with a chlorine atom to form sodium chloride?

   [1 mark]

   • ASodium gains one electron and chlorine loses one electron
   • BSodium loses one electron and chlorine gains one electron
   • CBoth atoms share a pair of electrons equally
   • DNo electrons move between the atoms

   (c)

   Explain, in terms of electronic structure, why a sodium atom forms a 1+ ion and a chlorine atom forms a 1- ion when they react together.

   [2 marks]

   Total for question 1: 4 marks

2. 2
   A dietary supplement manufacturer produces magnesium oxide tablets. Magnesium is in Group 2 of the periodic table and reacts with oxygen, in Group 6, to form the ionic compound magnesium oxide used in the tablets.

   (a)

   What charge would the magnesium ion have in magnesium oxide?

   [1 mark]

   • A1+
   • B1-
   • C2-
   • D2+

   (b)

   The manufacturer's quality control chemist explains that magnesium oxide, like sodium chloride, has high melting and boiling points. What is the main reason for this?

   [1 mark]

   • AStrong electrostatic forces of attraction between oppositely charged ions acting in all directions throughout the giant lattice
   • BWeak intermolecular forces between molecules
   • CDelocalised electrons moving freely through the structure
   • DWeak covalent bonds between individual atoms

   (c)

   Describe the structure of magnesium oxide as a giant ionic lattice, and explain why it does not conduct electricity in its solid state but does conduct electricity when molten.

   [2 marks]

   Total for question 2: 4 marks

3. 3
   A materials science student is studying calcium oxide, an ionic compound that is a key raw material in cement manufacturing. Calcium is in Group 2 of the periodic table and oxygen is in Group 6, and the student needs to explain how their atoms combine to form the ionic compound used industrially.

   (a)

   A materials science student is comparing calcium oxide, an ionic compound used in cement production, with the giant ionic lattice model. Calcium is in Group 2 and oxygen is in Group 6. Describe how a dot and cross diagram would represent the transfer of electrons from a calcium atom to an oxygen atom to form calcium oxide, and state the charges on the resulting ions.

   [3 marks]

   (b)

   The student then investigates calcium chloride, formed from calcium (Group 2) and chlorine (Group 7), which is used to de-ice roads in cold climates. Explain how the ionic bonding in calcium chloride differs from that in sodium chloride in terms of the ratio of ions, and deduce the formula of calcium chloride, showing your reasoning.

   [4 marks]

   Total for question 3: 7 marks

4. 4
   A geologist is examining rock salt deposits formed millions of years ago from the evaporation of ancient seas, leaving behind thick layers of sodium chloride crystals. The geologist is preparing an explanation for colleagues about why these deposits show high melting points, hardness and a tendency to shatter along flat planes when struck.

   (a)

   A geologist studying rock salt deposits formed from evaporated ancient seas wants to explain to colleagues, using sodium chloride as the main example, how ionic bonding forms and why it produces a solid with the specific physical properties observed in these mineral deposits, such as high melting point, hardness, and brittleness. Describe the formation of ionic bonds between metals and non-metals and explain how the resulting giant ionic lattice structure accounts for these properties.

   [6 marks]

   (b)

   The geologist also wants to explain why rock salt deposits do not conduct electricity when dry and solid, but boreholes drilled into these deposits and flooded with water to dissolve the salt (a technique called solution mining) produce a conducting solution used to extract the salt. Explain, in terms of the behaviour of ions, why solid ionic compounds do not conduct electricity but aqueous solutions of ionic compounds do, and evaluate why this property makes solution mining an effective extraction method for underground salt deposits.

   [6 marks]

   Total for question 4: 12 marks

End of questions